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.Dd Oct 19, 2004
.Dt GETXATTR 2
.Os "Mac OS X"
.Sh NAME
.Nm getxattr,
.Nm fgetxattr
.Nd get an extended attribute value
.Sh SYNOPSIS
.Fd #include <sys/xattr.h>
.Ft ssize_t
.Fn getxattr "const char *path" "const char *name" "void *value" "size_t size" "u_int32_t position" "int options"
.Ft ssize_t
.Fn fgetxattr "int fd" "const char *name" "void *value" "size_t size" "u_int32_t position" "int options"
.Sh DESCRIPTION
Extended attributes extend the basic attributes of files and
directories in the file system.  They are stored as name:data pairs
associated with file system objects (files, directories, symlinks, etc).
.Pp
The
.Fn getxattr
function retrieves up to
.Fa size
bytes of data from the extended attribute identified by
.Fa name
associated with
.Fa path
into the pre-allocated buffer pointed to by
.Fa value .
The function returns the number of bytes of data retrieved.
.Pp
An extended attribute's
.Fa name
is a simple NULL-terminated UTF-8 string.
.Fa position
specifies an offset within the extended attribute.  In the current
implementation, this argument is only used with the resource fork attribute.
For all other extended attributes, this parameter is reserved and should
be zero.
.Pp
On success,
.Fa value
contains the data associated with
.Fa name .
When
.Fa value
is set to NULL,
.Fn getxattr
returns current size of the named attribute.  This facility can be used
to determine the size of a buffer sufficiently large to hold the data
currently associated with the attribute.
.Pp
.Fa options
specify options for retrieving extended attributes:
.Pp
.Bl -tag -width XATTR_NOFOLLOW
.It Dv XATTR_NOFOLLOW
do not follow symbolic links.
.Fn getxattr
normally returns information from the target of
.Fa path
if it is a symbolic link.  With this option,
.Fn getxattr
will return extended attribute data from the symbolic link instead.
.It Dv XATTR_SHOWCOMPRESSION
.Fn getxattr
and 
.Fn fgetxattr
will return HFS Plus Compression extended attribute
.Fa name
(if present) for the file referred to by
.Fa path
or
.Fa fd .
.El
.Pp
.Fn fgetxattr
is identical to
.Fn getxattr ,
except that it retrieves extended attribute data from the open file
referenced by the file descriptor
.Fa fd .
.Sh RETURN VALUES
On success, the size of the extended attribute data is returned.  On
failure, -1 is returned and the global variable
.Va errno
is set as follows.
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er ENOATTR
The extended attribute does not exist.
.It Bq Er ENOTSUP
The file system does not support extended attributes or has the feature
disabled.
.It Bq Er ERANGE
.Fa value
(as indicated by
.Fa size )
is too small to hold the extended attribute data.
.It Bq Er EPERM
The named attribute is not permitted for this type of object.
.It Bq Er EINVAL
.Fa name
is invalid or
.Fa options
has an unsupported bit set.
.It Bq Er EISDIR
.Fa path
or
.Fa fd
do not refer to a regular file and the attribute in question is only
applicable to files.  Similar to EPERM.
.It Bq Er ENOTDIR
A component of
.Fa path 's
prefix is not a directory.
.It Bq Er ENAMETOOLONG
The length of
.Fa name
exceeds
.Dv XATTR_MAXNAMELEN
UTF-8 bytes, or a component of
.Fa path
exceeds
.Dv NAME_MAX
characters, or the entire
.Fa path
exceeds
.Dv PATH_MAX
characters.
.It Bq Er EACCES
Search permission is denied for a component of
.Fa path
or the attribute is not allowed to be read (e.g. an ACL prohibits reading
the attributes of this file).
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
.It Bq Er EFAULT
.Fa path
or
.Fa name
points to an invalid address.
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.El
.Sh SEE ALSO
.Xr listxattr 2 ,
.Xr removexattr 2 ,
.Xr setxattr 2
.Sh HISTORY
.Fn getxattr
and
.Fn fgetxattr
first appeared in Mac OS X 10.4.
